The present invention relates to a method for repairing a circuit connection part where a large number of opposed circuits are connected electrically through an adhesive.
Recently, in the field of precision electronic machines, the density of circuits is becoming higher, and therefore a failure of electrical connection due to removal, peeling or displacement of wiring, or a failure of electronic parts or circuits after connection of the circuits, frequency occurs. Thus, for solving such a problem, a method has been employed in which the circuits are separated from one another by, for example, peeling off, and a residue of the adhesive remaining on or between the circuits is removed using a buffing rotor impregnated with an organic solvent (Japanese Provisional Patent Publication No. 223945/1994) or using a composition for removing an adhesive (Japanese Provisional Patent Publications No. 080939/1994 and No. 080940/1994), followed by connection of the circuits (hereinafter referred to as xe2x80x9creconnectionxe2x80x9d) using a new adhesive.
However, the above methods for removing an adhesive require long-time operations, and it is extremely difficult to completely remove the adhesive remaining in fine portions. Further, the circuit members are exposed to the organic solvent used for removing the adhesive for a long period of time, leading to problems that the dimensional precision of the circuit members becomes poor and removal of a circuit terminal occurs. In addition, when the removal of the adhesive is insufficient or the solvent used causes the electronic parts or the substrate material for the circuit to be repaired to suffer corrosion, problems of a connection failure after reconnection and a lowering of the reliability of connection arise.
The present invention provides a method for removing an adhesive, repair of which has previously required a long period of time, within a short period of time and without damaging the circuit members.
There is provided a method for repairing a circuit connection part where circuit members having a large number of opposed circuits are connected electrically through an adhesive, wherein mutual joints at a circuit connection part requiring repair are separated, a basic material for transfer is bonded through a transfer adhesive for transfer to at least one circuit member where the adhesive remains, and then the adhesive remaining on the circuit member and the transfer adhesive are removed from the circuit member along with the basic material for transfer.
A place where remaining adhesive is removed or peeled off is an interface between the circuit member, and the transfer adhesive and the remaining adhesive.
The present invention is a method for repairing a circuit connection part, in which the adhesive can be removed, within a short period of time and without using any solvent, from the circuit member that has conventionally been repaired using a solvent inevitably, and the present invention can markedly improve the reliability of reconnection.
With respect to the transfer adhesive used in the present invention, any adhesive described in xe2x80x9cAdhesion Handbookxe2x80x9d (2nd edition, published by Nikkan Kogyo Shimbun Ltd., edited by The Adhesion Society of Japan), Item II, Column of ADHESIVE, can be preferably used. As the adhesive for bonding together circuit members, an epoxy resin type adhesive is mainly used, and an epoxy resin type transfer adhesive is more preferred because it is expected that the epoxy resin type transfer adhesive strongly adheres to an anisotropic conductive adhesive. Further, when the anisotropic conductive adhesive itself is used as a transfer adhesive, it is especially preferred since it is adhesion of the same kinds of adhesives and the adhesive force therebetween is excellent. The transfer adhesive may be either of a liquid form or of a film form, and the transfer adhesive of a film form is preferred since it has more excellent working properties than those of a liquid form.
With respect to the basic material for transfer used in the present invention, there is no particular limitation as long as the adhesion strength between the basic material for transfer and the transfer adhesive is larger than the adhesion strength between the circuit member to be repaired and the adhesive. For example, there can be preferably used metals and glass each having a surface roughened by an acid or an alkali, metals and glass each having a surface activated by a plasma, ultraviolet, or corona discharge treatment, plastics such as epoxy resins, acrylic resins, polyethersulfone, polyimide and polypropylene, reinforced base materials obtained by impregnating the above plastics into glass woven fabric, and plastics each having a surface activated by a plasma, ultraviolet or corona discharge treatment. The term xe2x80x9cmetalxe2x80x9d used here means any one of elements belonging to Groups 1 and 11 (alkali metals and copper group) exclusive of hydrogen, elements belonging to Groups 2 and 12 (alkaline earth metals and zinc group), elements belonging to Group 3 exclusive of boron, elements belonging to Group 4 exclusive of silicon, and elements belonging to Groups 8 to 10 (iron group and platinum group) and to Groups 5 to 7 (respective sub-a groups of Groups V, VI, and VII) of the Periodic Table, and alloys of at least two elements selected from the above elements, each of which has a higher melting point than the heating temperature for removing the circuit to be repaired from the base material for transfer.
In the present invention, when the circuit to be repaired is removed from the base material for transfer, the circuit connection part can be advantageously repaired by peeling off at the condition of xe2x88x9220xc2x0 C. to 400xc2x0 C. The higher the temperature, the lower the adhesion strength, and therefore, it is preferred that the circuit is removed at 100xc2x0 C. to 400xc2x0 C. since the damage of the circuit can be suppressed, and it is more preferred that the circuit is removed at 150xc2x0 C. to 300xc2x0 C. since not only can the damage of the circuit be suppressed, but also the circuit to be repaired is unlikely to suffer heat deformation.
Further, it is more preferred that heating is conducted from the side of the circuit member to be repaired, because a temperature gradient is caused and the temperature of the interface between the circuit member and the adhesive is higher than the temperature of the interface between the transfer adhesive and the base material for transfer; namely, the degree of lowering of the adhesion strength between the circuit member and the adhesive is larger than the degree of lowering of the adhesion strength between the transfer adhesive and the base material for transfer, thus enabling the adhesive remaining on the circuit member to be easily transferred.
According to the present invention, not only can the circuit member to be repaired be advantageously repaired within a short period of time without using any solvent and without causing the circuit to suffer any damage, but also the circuit member repaired can be remarkably improved in the reliability of the connection after reconnection.